We hope to account for the previously-demonstrated individual differences in rat general activity under conditions of high ambient temperature by relating them to the circadian variation of core temperature. Further, we will examine the dissociation of the temperature rhythms of activity, eating, and drinking, under conditions of light:dark reversal. We will extend our previous comparison of period of running cycle under conditions of continuous illumination and of reversal of light:dark, by working from a base of LD 14:10 instead of LD12:12. This should yield a more dependable picture of the resetting process that presumably underlies period length in both situations. We hope also to continue our studies of ulceration caused by inescapable electric shock, examined under free-running (e.g., continuous darkness) conditions as well as LD12:12.